Transforming 3G radio Access Architecture

Ionut BIBAC & Emmanuel DUJARDIN

Agenda

Main Triggers for New Access Architecture Toward Flat Architecture: Issue and Limitation The 3M of beyond 3G: Multi-Carrier, Multi-Antenna

(MiMo) and Multi-Layer One Word on SDR… Conclusion

Main Triggers for Deploying New Access Architecture

Access to a larger (and variable) spectrum allocation Higher spectrum efficiency which implies:

Reduction latency with a better QoS and user experience Variable channel BW and harmonized FDD/TDD enables greater flexibility to exploit different band allocations. Spectrum reframing where we can take advantage of the flexible channel BW and/or better potential use of TDD spectrum.

Optimized for flat architecture (should leave to lower cost network in the long term) Not burdened by need to support legacy terminals and protocols leads to optimized

spectrum efficiency and latency performance. Higher capacity per site should lead to lower cost/bit at high traffic levels. Capability to support new service and/or competition with other technologies that

requires the lower latency of LTE to achieve good/equivalent customer satisfaction.

Towards Flat Architecture

flat architecturefewer layers of network elements (collapsed architectures)fewer central bottlenecksmore any to any connectivity

drivers / expected benefits (to be confirmed)costs: lot of small not redundant units cheaper than few central high capacity, highly reliable network elements (including hosting costs)performance: traffic go through fewer equipments, more direct routes => less latency, jitter, better throughput

Examples:LTE/EPCHSPA flat architecture / I-HSPADirect Tunnelfemtocells

3G – LTE/EPC – HSPA Flat

NB RNC SGSN

MSC

GGSN Data

PSTN

eNBServing

GatewayPDN

GatewayData

MME

HLR

HLR

3G:

LTE/EPC (3GPP R8):

HSPA Flat Architecture (3GPP R8 option) / I-HSPA:

NB/RNC

RNC

SGSN

MSC

GGSN Data

PSTN

HLR

Direct Tunnel - Femto

NB RNC

SGSN

MSC

GGSN Data

PSTN

HLRDirect Tunnel: (3GPP R7)

NB/RNC

RNC

SGSN

MSC

GGSN Data

PSTN

HLR

Direct Tunnel + HSPA Flat:

HNB= ~NB/RNC

FGW SGSN

MSC

GGSN Data

PSTN

HLR

Femto (not standard yet):

Issue and Limitations of Flat Architecture

data only (except femto*): if voice on circuit, feasibility and performance to be checked (for example on I-HSPA):

About Femto: most issues are currently handled with a gateway/proxy that hides complexity from CN…but not really flat..though collapsed

signalling: all mobility is managed at CN level => either CN correctly designed to handle it (EPC?) or best fitted for slow moving users

Security:any to any connectivity assumes IP transport network, could be 3rd party network or even public internetcollapsing RNC functions into NB involves that radio ciphering is done in NBdirect connection to CN equipments (except femto*)

impact on existing equipments (configuration and interface): more network nodes visible (except femto*)

interworking and interconnections to legacy architectures need to have a centralized point of interconnection

The 3M of beyond 3G: Multi-Carrier

–…

–Sub-carriers–FFT

–Time

–Symbols

–5 MHz Bandwidth

–Guard Intervals

–…

–Frequency

OFDM basic principlesCarrier (e.g. 5 MHz) is subdivided into many narrower band sub-carriers with lower ratesUser receives many sub carriers together to achieve higher ratesDesigned to achieve low distortion on each sub-carrier due to radio reflections and adjacent sub-carriers

The 3M of beyond 3G: Multi-Antenna (Mimo)

MIMO = Canal matriciel

xi : Signaux émisYi : Signaux reçus

x1

x2

xN

y1

y2

yN

Problème du récepteur:Retrouver signaux émis X

X = H-1 Y

N canaux de' transmission parallèles

Possible si H est inversible

Eléments hij décorrélés

Conditions les plus favorables:Milieu très réflectif

Plutôt Indoor

The 3M of beyond 3G: Multi-Layer

One Word on SDR…

Software Defined Radio stands for a radio technology agnostic Hardware platform in which some or all Radio and Baseband functionalities are controlled by Software.

Early GSM specifications, about filters and frequency blocking, are challenging.Some demand for relaxation of the band.

Difficulty to precisely estimate today the necessary processing power for a later use, towards LTE for instance and ultimately any other new usage.

Coexistence of technologies in same modules is not easy to manage.

Vendors are tied with their current chipset choices. Moving to fully SW defined platform means initially full re-development of firmware. On the other hand they gain full flexibility on future development.

Roadmaps shows no OSS evolution with SDR introduction. For instance, changing the technology is done by deletion & recreation of cells, all of the earlier settings and optimisations are lost. SDR cannot (yet) be considered as a dynamic configuration enabler

Conclusion

Operator benefits of the new air interface Access to larger (and variable) spectrum allocations Higher spectrum efficiency: lower cost per bit Reduced latency: better QoS ans user experience

Reasons for migration Higher spectrum efficiencies can also be achieved by HSPA+ with lower migration cost (assuming 5 MHz spectrum allocation) New spectrum allocations or re-farming may motivate migration (currently 20 MHz allocations seem very unlikely but 10 MHz may be possible) E-UTRAN will be deployed together with evolved packet core (EPC)

Air Interface evolution will continue IMT advanced seems far away for operators. Concurrent systems are in starting blocks so 3GPP also has to respond.